クリスタルメイル [crystal mail] in Japanese.
Final Fantasy I
Stats: DEF +44, EVA -10
Equip: ?
Obtain: ?
Description: Mail of crystal, crafted long time ago
Final Fantasy III

Stats: DEF 55, MDEF 24, weight 1
Use: FRE, ONK, WAR, RDM, KNT, DRG, VIK, DRK
Buy: 50,000 gil (sell: ? gil)
Shop: Eureka
Treasure: Ancients' Maze, Crystal Tower
Type: Body
Final Fantasy IV
Stats: DEF 25, MDEF 10, EVA 0, MEVA 6, MND +3
Equip: Cecil
Buy: - (sell: 12,000 gil)
Treasure: Lunar Subterrane B5
Other: prevents berserk, blind, mini, pig, silence and toad
Final Fantasy V
Note that in a completely inexplicable move, the Crystal Mail in FF5 was called Crystal Armor in the English translation.
Final Fantasy VI
Stats: DEF
Equip: Celes, Cyan, Edgar, Locke, Setzer, Terra
Obtain: ?
Description: Resplendent suit of crystal mail
Final Fantasy Tactics
Stats: HP +110
Equip (job): Knight, Dragoon, Samurai, Dark Knight, Onion Knight
Equip (character): Squire (Ramza, ch2+), Fell Knight, Holy Knight, Game Hunter, Templar, Sky Pirate, Sword Saint, Divine Knight, Ark Knight
Equip (enemy): level 37
Buy: 19,000 gil (sell: 9,500 gil)
Shop: (available after Fort Besselat ch4) Lesalia, Castles
Description: Platinum armor reinforced in places with crystalline gemstones found deep within the earth.
Other: other jobs can equip with Equip Heavy Armor
Crystal Chronicles
Stats: DEF +24
Equip: all races
Buy: Radiant Armor -scroll, Mythril, Tiny Crystal, 500 gil
Other: resist Miasma
Pictlogica

Stats (lv1): HP +60, STR +40
Buy: - (sell: ? gil)
Obtain: event quest Doga's Cave
Type: Accessory, Rarity: ★★★★★, Element: -
Record Keeper

Crystal Mail (V)
Stats: DEF +52, MDEF +22, EVA 102 (lv1), ? (lv5), ? (lv10), ? (lv15), ? (lv20), DEF +101, MDEF +52, EVA 102 (lv25)
Max Level: lv15 (initial), lv20 (first evolve), lv25 (second evolve)
Type: Heavy Armor, Rarity: ★★★★

Crystal Mail (VI)
Stats: DEF +83, MDEF +40, EVA 102 (lv1), ? (lv5), ? (lv10), ? (lv15), ? (lv20), ? (lv25), DEF +128, MDEF +65, EVA 102 (lv30)
Max Level: lv20 (initial), lv25 (first evolve), lv30 (second evolve)
Type: Heavy Armor, Rarity: ★★★★★
Other: enables use of the Provoke Soul Break when equipped
Category: Equipment